Toxicity to Fishes of Insecticides Used in Paddy Fields and Water Resources I. Laboratory Experiment

Abstract

The toxicity test of pesticides used in paddy fields and water resources was made against one month old fish in jars containing 4000 cc. of water each in a laboratory. The insecticides were applied directly into water and they were mainly in granulated form which included aldicarb 10 G, biothion 5 G, BHC 6 G, BHC-carbaryl mixture 16 G, carbaryl 10 G, chlorpyrifos 40.8 E.C., diazinon 10 G, dioxacarb 50 W.P., disulfoton 5 G, fenitrothion 1000 E, fenitrothion-malathion mixture 1000 E, heptachlor 10 G, isoprocarb 50 W.P., malathion 1000 E, phorate 10 G, phosfolan 5 G, and propoxur 5 G. The mosquito fish, Gambusia holbrooki (Smith), walking catfish, Clarius batrachus (Linn.), nile tilapia, Tilapia nilotica Linn., common carp, Cyprinus carpio Fab and in some cases the snake skin gourami, Trichogaster pectaralis Reg. were used in this experiment. Fish showed the same major toxic symptoms as affected by the tested insecticides. Swimming was first excellerated and later on lost its control of direction. Curves bodies and haemorhagic symptoms along gills and stomach were apparent after death. The mosquito fish which lives mainly along water surface showed higher resistant to most tested insecticides even in the LVC form. The walking catfish with the bottom feeder habitat, on the other hand, showed the most susceptible to most tested chemical. The toxicity of the tested insecticides as determined by LC50s ranged from high to low to the following fishs were as follows : for the snake skin gourami, chlorpyrifos, aldicarb, isoprocarb, BHC-carbaryl mixture, and dioxacarb respectively; for the nile tilapia, chlorpyrifos, phorate, disulfoton E.C., BHC, cabaryl, aldicarb, isoprocarb, disulfoton G, heptachlor, phosfilan, propoxur, BHC-carbaryl mixture, dioxacarb, and biothion respectively; for the common carp, chlorpyrifos, disulfoton E.C., phorate, aldicarb, BHC, carbaryl, disulfoton G, heptachlor, propoxur, isoprocarb, phosfolan, BHC-carbaryl micture, dioxacarb and biothion respectively; for the mosquito fish, disulfoton E.C., phorate, heptachlor, cabaryl, BHC, propoxur, fenitrothion, disulfoton, fenitrothion-malathion mixture, malathion, diaznon, phosfolan, and biothion respectively ; and for the walking catfish, disulfoton E.C., BHC, phorate, carbaryl, heptachlor, malathion, fenitro-thion-malthion mixture, phosfolan, propoxur, fenitrothion, disulfonton, diazinon, and biothion respectively. Insecticides which their recommended rates of application caused acute toxicity to fishes were alsicarb, BHC, carbaryl, chlorpyrifos, disulfoton, heptachlor, and phorate. They should not be used in the pest control in paddy fields and water resources.